Start on a lower rim and work your way up. We spent a lot of time working on this in HS and it paid off. You need the right combination of height, jumping ability, timing and ball control; but if you suck at one of these it isn't going to happen. Note: Good shoes and a sticky floor will help on your first real dunk unless you're a freak, and I assume you're not.
Once you've acheived your goal, wait until your playing hoops with your friends to bust out your new talent, then break one off on your friend Mitch or Chet, you'll be a legend. Good luck.
:shocked: